Soil survey geological evidences and lack of human occupation artefacts led scientists to formulate the claim that the Netherlands was largely underwater between the 3rd century and 1050. This is the so-called third Dunkirk Transgression.
The reality of the events, hypothetically determined by cyclical phases of strong sea level rises in historical times, is debated.
The low-lying continental coast of Europe was lightly populated until c. 200 BC, when the climate and environment became more amenable to human habitation. Conditions remained favourable from 200 BC to 250 AD, and the region became densely populated.
However the region had been undergoing a series of marine transgressions (called Dunkirk 0 through Dunkirk IIIb) characterised by a rising water table and floods that left layers of clay on the land. The heaviest blow came with the "Dunkirk II transgression" that began in the 3rd century and continually worsened, leaving large areas of the coast uninhabitable from c. 350–c. 700. People were forced to abandon their homes and emigrate. Archaeologists conducting research along the historically flood-prone coast tell this same story for The Rhine/Meuse delta (Zeeland, Brabant, parts of South Holland and Limburg); Friesland; Groningen; Ostfriesland, German Friesland and the Weser/Jade estuary; and Dithmarschen, Eiderstedt and Nordfriesland.
In the Rhine/Meuse delta, the population became scanty. Between the 5th and 7th centuries there were few centers of occupation in the delta region, and in the estuarine and peat areas no settlements at all have been found. The area would not be repopulated until the Carolingian Era. The areas with river clay were so covered with sedimentation that habitation was almost impossible between 250–650.
- Louwe Kooijmans 1974:44–45, The Rhine/Meuse Delta.
- Ejstrud 2008:17–19, The Migration Period.
- Knottnerus 2001:30–31, LANCEWAD 2001: Cultural History.
- Meier 2004:55,63, Man and Environment in Schleswig-Holstein.
- Louwe Kooijmans 1974, The Rhine/Meuse Delta, PhD Thesis.
- Louwe Kooijmans 1980:106–133, Archaeology and Coastal Change in the Netherlands.
- Nienhuis 2008, Environmental History of the Rhine-Meuse Delta.
- Knottnerus 2001:29–63, Cultural History in LANCEWAD: Landscape and Cultural Heritage in the Wadden Sea Region—Project Report.
- Meier 2004:55–70, Man and environment in the marsh area of Schleswig-Holstein from Roman until late Medieval times.
- Meier, Landscape and Settlement History of the North-Sea Coast of Schleswig-Holstein.
- Louwe Kooijmans 1974:44, The Rhine/Meuse Delta.
- Louwe Kooijmans 1974:120, The Rhine/Meuse Delta.
- Rising seas around the shores of Holland in the late Roman period by the Society for Interdisciplinary Studies, The oldest and most up to date society for catastrophist information and research, 2010
- Sea level rise, transgression phases and storm surges in maritime Flanders to the end of the 16th century. A study of the landscape, ecology and climate from a historical point of view. Dr. Beatrijs Augustyn, (English summary of the general conclusion of the thesis by B. Augusyn, Zeespiegelrijzing, transgressiefasen en stormvloeden in maritiem Vlaanderen tot het einde van de XVIde eeuw. Een landschappelijke, ecologische en klimatologische studie in historisch perspektief, Brussel, Algemeen Rijksarchief, Studia 37-38), 1992 PDF